Vibrotactile intensity DLs were measured by the continuous pedestal and
gated pedestal methods. In both cases, the relative DL decreased as a function
of the sensation level of the stimulus and the results, in most cases, could be
described as a near miss to Weber's law. DLs measured by the continuous
pedestal method were found to decrease substantially as a function of increases
in stimulus duration over a range of 12 to 1000 ms and the results could be
described by a temporal summation function derived from Zwislocki's theory of
temporal summation [J. J. Zwislocki, J. Acoust. Soc. Am. 32, 1046--1060
(1960)]. In contrast, DLs measured by the gated pedestal method were only
slightly affected by changes in stimulus duration. These findings are
consistent with the hypothesis that, at suprathreshold levels of stimulation,
the effects of temporal summation tend to be cancelled by the effects of
adaptation.